The EEG is comprised of rhythmic activity oscillating at different frequencies. This rhythmic activity is theorized to emerge from interactions between the thalamus and cortex (see Pizzagalli, 2007, for review). For adults, specific frequency bands (e.g., 4–8 Hz; 8–13 Hz) are associated with different behaviors or mental processes. One challenge for developmental EEG researchers is understanding how infant/child frequency bands are related to adult frequency bands. As can be seen in Figure 2, there are differences in both the frequency and amplitude of infant and adult EEG. Early longitudinal research demonstrated that (a) infant EEG is at a much lower frequency than adult EEG and (b) there are substantial changes in the peak frequency from infancy through early childhood (see Bell, 1998; Bell & Fox, 1994, for reviews). Accordingly, developmental EEG researchers have questioned the appropriateness of using traditional adult frequency bands (Pivik et al., 1993).
